1. Field of the Invention
The present invention relates to wireless communication. More particularly, the present invention relates to an apparatus and method for reducing power consumption in mobile terminals.
2. Description of the Related Art
Mobile terminals were developed to provide wireless communication between users. As technology has advanced, mobile terminals now provide many additional features beyond simple telephone conversation. For example, mobile terminals are now able to provide additional functions such as an alarm, a Short Messaging Service (SMS), a Multimedia Message Service (MMS), E-mail, games, remote control of short range communication, an image capturing function using a mounted digital camera, a multimedia function for providing audio and video content, a scheduling function, and many more. With the plurality of features now provided, a mobile terminal has effectively become a necessity of daily life.
A sleep mode is a state in which an Advanced Mobile Station (AMS) conducts pre-negotiated periods of absence from the serving Advanced Base Station (ABS) air interface. An AMS may activate sleep mode when the AMS is in the connected state. When the sleep mode is active, the AMS is provided with a series of sleep cycles. Each sleep cycle typically includes a listening window followed by a sleep window.
During the sleep window, the ABS does not transmit any data to the AMS. The AMS may power down one or more physical operation components or perform other activities that do not require communication with the ABS.
During the listening window, the AMS is typically expected to receive all Downlink (DL) transmissions in the same way as in the state of normal operations. The AMS generally ensures that it has up-to-date system information for proper operation. The synchronization and system configuration information acquisition and verification may be done by waking up at the super frame header just prior to the frame in which its listening window is located to ensure that the super frame number and the system configuration description change count are as expected. Upon wakeup from sleep state, if the AMS detects that it is not synchronized, or the AMS detects a different ABS, the AMS exits sleep mode and performs network re-entry. If the AMS detects that the information it has is not up-to-date, then the AMS does not transmit in the Listening window until the AMS receives up-to-date system information.
The length of successive sleep cycles may remain constant or may be adaptive based on traffic conditions. Sleep windows and listening windows may also be dynamically adjusted for the purpose of data transportation as well as for MAC control signaling transmission. The AMS may send and receive data and MAC control signaling without deactivating sleep mode.
However, existing sleep mode schemes are inefficient in that, under some circumstances, the AMS may extend the listening window unnecessarily, thereby increasing power consumption. Accordingly, there is a need for an apparatus and method for improving power saving while operating in a sleep mode.